TPE Injection Moulding: Thermoplastic Elastomer Material Guide
Thermoplastic elastomer (TPE) delivers rubber-like flexibility and soft-touch feel while being processable on standard injection-moulding equipment without vulcanisation. It is the material of choice for grips, seals, soft-touch over-moulding, and any part that must flex repeatedly without fatigue. Nordmould moulds TPE as a standalone material and as the second shot in two-component over-moulding, for series from 100 pieces.
What are the mechanical and thermal properties of TPE?
TPE is not a single material but a family of several distinct chemistries. The most common injection-moulding grades are styrenic block copolymers (SBS and SEBS), followed by thermoplastic vulcanisates (TPV) and thermoplastic polyester elastomers (TPE-E / COPE). Properties vary widely with grade and hardness.
| Property | SEBS (Shore 40A) | SEBS (Shore 60A) | TPV (Shore 55A) | TPE-E (Shore 40D) |
|---|---|---|---|---|
| Tensile strength | 3–8 MPa | 6–12 MPa | 5–10 MPa | 20–35 MPa |
| Elongation at break | 400–800 % | 300–600 % | 300–600 % | 200–400 % |
| Compression set (22 h / 70 °C) | 20–35 % | 15–30 % | 15–25 % | 20–40 % |
| Continuous service temp | −40 to 100 °C | −40 to 110 °C | −40 to 120 °C | −40 to 130 °C |
| Water absorption (24 h) | < 0.1 % | < 0.1 % | < 0.1 % | 0.2–0.5 % |
| Density | 0.88–1.00 g/cm³ | 0.90–1.02 g/cm³ | 0.95–1.05 g/cm³ | 1.15–1.25 g/cm³ |
| Shrinkage | 0.5–2.5 % | 0.5–2.5 % | 0.8–2.0 % | 0.8–1.8 % |
Compression set — the degree to which a compressed elastomer fails to recover its original thickness — is a key performance metric for seals and gaskets. TPV grades typically offer better compression-set recovery than standard SEBS.
What are the typical applications of TPE injection moulding?
TPE's rubberiness, colour range, and compatibility with hard-plastic over-moulding make it ubiquitous across consumer, medical, and industrial product design.
Soft-touch over-moulding: Power tool handles, toothbrush handles, kitchen utensil grips, and consumer electronics controls all use TPE over-moulded onto rigid ABS, PP, or nylon substrates. The combined part achieves structural rigidity from the hard substrate and ergonomic comfort from the TPE layer. Nordmould performs two-shot over-moulding or insert-moulding of pre-formed rigid parts followed by TPE encapsulation.
Seals and gaskets: Softer TPE grades (Shore 20A–40A) are used for static seals, dust-exclusion gaskets, and water-resistant membranes in consumer electronics and automotive trim. TPV is preferred over SEBS where higher continuous service temperatures or better compression-set recovery are needed.
Medical and personal care: TPE grades meeting ISO 10993 biocompatibility requirements are used for syringe plungers, mask seals, soft-tip instruments, and baby products. The absence of plasticisers (unlike PVC) is an advantage in many health-related applications.
Footwear and apparel hardware: Shoe soles, buckles, and garment clips use TPE for its balance of flexibility, durability, and colourability.
Automotive: Interior soft-touch trim elements, armrest skins, and under-bonnet vibration dampeners use TPV for higher service temperatures.
How is TPE processed in injection moulding?
TPE processes on standard injection moulding equipment with no special tooling. Key differences from rigid plastics are the lower hardness (requiring careful ejection design) and sensitivity to gate position in over-moulding applications.
| Processing parameter | SEBS / SBS | TPV | TPE-E |
|---|---|---|---|
| Melt temperature | 170–220 °C | 190–230 °C | 220–260 °C |
| Mould temperature | 20–40 °C | 20–50 °C | 20–60 °C |
| Injection pressure | 35–100 MPa | 50–100 MPa | 50–120 MPa |
| Shrinkage | 0.5–2.5 % | 0.8–2.0 % | 0.8–1.8 % |
| Recommended draft angle | ≥ 2° per side | ≥ 2° per side | ≥ 1° per side |
Gate design for over-moulding: the gate should be positioned to allow TPE to flow uniformly over the rigid substrate, avoiding trapped air pockets. Fan gates or multiple pin-point gates work better than a single centre gate for wide parts. Nordmould evaluates gate position during the DFM review for all over-moulding projects.
Ejection: soft TPE parts require generous draft angles (2° minimum, 3° preferred for very soft grades) and smooth-polished ejection areas. Stripper rings or sleeve ejectors perform better than pin ejectors on thin-walled soft parts.
Bonding in over-moulding: mechanical interlocks (through-holes, undercuts, or window features in the rigid substrate) provide additional adhesion beyond chemical bonding, especially for parts subject to peeling forces. Nordmould designs mechanical bond features into the substrate where the chemical bond is borderline.
What grades and variants of TPE are available?
| Family | Key feature | Typical use case |
|---|---|---|
| SBS (styrenic) | Low cost, good clarity | Soft toys, disposable grips |
| SEBS (styrenic, saturated) | UV and heat stability over SBS | Outdoor grips, over-moulding |
| TPV (thermoplastic vulcanisate) | Low compression set, heat resistance | Seals, gaskets, automotive |
| TPE-E / COPE | High strength, oil resistance | Structural flexible parts, connectors |
| TPE-A (PEBA) | Very wide temperature range | Ski boots, sports equipment |
| Medical-grade SEBS | ISO 10993 biocompatible | Medical devices, baby products |
Nordmould sources SEBS and TPV as primary injection-moulding grades; TPE-E, TPE-A, and speciality medical grades can be sourced on request through our material partner network.
What are the advantages and limitations of TPE?
Advantages:
- Rubber-like flexibility and soft touch without vulcanisation
- Reprocessable and recyclable — unlike thermoset rubbers
- Wide hardness range (Shore 20A to Shore 70D) from a single material family
- Excellent over-moulding adhesion to PP and ABS substrates
- No odour issues in food-contact or consumer applications (unlike some PVC)
- Fast tooling qualification — same tooling and equipment as rigid plastics, no vulcanisation cure time
Limitations:
- Compression set performance is inferior to vulcanised rubber for demanding seal applications
- Softer grades (Shore 20A–40A) can be difficult to eject cleanly without generous draft
- Some TPE families have limited resistance to oils, fuels, and aromatic solvents
- Tensile strength is much lower than rigid engineering plastics — not load-bearing
- Long-term creep under sustained load is significant in softer grades
- TPE is not a single material; selecting the wrong family for chemical environment or temperature range is a common design error
When should you choose TPE over alternative materials?
Choose TPE over silicone when moulding by injection (silicone requires liquid injection moulding equipment), when cost is a driver (silicone is significantly more expensive per kilogram), or when the part will be over-moulded onto a thermoplastic substrate. Silicone outperforms TPE at continuous service temperatures above 120 °C and in medical implant applications.
Choose SEBS over SBS for any application with UV exposure or service temperatures above 70 °C. SBS degrades and discolours relatively quickly outdoors. The cost premium for SEBS is small.
Choose TPV over SEBS for seals and gaskets where low compression set is required, especially above 80 °C. SEBS has adequate compression-set recovery at room temperature but deteriorates faster under elevated-temperature sustained compression.
Choose TPE over TPU when cost, ease of processing, and soft-touch feel are the primary requirements. TPU offers better abrasion resistance, higher tensile strength, and better oil resistance — use TPU when the part is a wheel, a seal in an oily environment, or a structural flexible component.
Recyclability and sustainability
TPE is thermoplastic and fully reprocessable. Unlike vulcanised rubber, which is irreversibly cross-linked, TPE can be remelted at end of life. In-process regrind (sprues, runners, reject parts) can be reblended at up to 15–20 % in most SEBS and TPV grades without significant property loss. Post-consumer TPE recycling is technically feasible but practically limited by collection and sorting infrastructure. Bio-based TPE grades with partial renewable carbon content are available for sustainability-driven projects.
Contact Nordmould with your part geometry and hardness requirement — a free DFM review will cover grade selection, over-moulding bond compatibility, draft analysis, and an indicative quote returned within one business day.
Frequently asked questions
What Shore hardness range is available for TPE injection moulding?
TPE is available across a very wide hardness range, typically Shore 20A to Shore 70D, depending on the formulation family. For soft-touch over-moulding, Shore 40A–60A is common. For structural-flexible hybrid parts, harder grades around Shore 50D are used. Nordmould helps specify the correct hardness during the DFM review.
Can TPE be over-moulded onto rigid plastic substrates?
Yes. Over-moulding TPE onto rigid substrates (ABS, PP, PC, nylon) is one of the most common two-shot or insert-moulding applications at Nordmould. Compatibility between the TPE grade and the substrate is critical — styrenic TPEs (SEBS, SBS) bond well to PP and ABS; other families may need adhesion promoters. Material compatibility is confirmed during the DFM review.
Does TPE require drying before injection moulding?
Most TPE grades have low moisture sensitivity, but manufacturer datasheets should always be checked. Styrenic block-copolymer TPEs (SEBS/SBS) generally do not require pre-drying. Polyester-based TPE-E grades should be dried at 80–100 °C for 2–4 hours. Nordmould follows resin-specific drying requirements as standard.
What is the difference between TPE and TPU for injection moulding?
TPE is a broad family of rubber-like thermoplastics; TPU (thermoplastic polyurethane) is one specific chemistry within that family but is typically classified separately due to its superior mechanical properties. TPE (especially SEBS grades) excels in soft-touch feel and ease of processing. TPU offers higher tensile strength, better abrasion resistance, and better oil resistance. Nordmould supplies both.
Can TPE parts be recycled?
Yes. TPE is thermoplastic and can be remelted and reprocessed, unlike vulcanised rubber. Sprues and runners from TPE moulding can be reground and reblended. TPE parts at end of life are recyclable in principle, though collection streams depend on the specific formulation. Nordmould can advise on regrind-compatible grades.
What wall thickness is recommended for TPE injection-moulded parts?
TPE wall thickness of 1.5–5.0 mm is typical. Very thin walls (under 1.0 mm) can be achieved in softer grades with hot-runner systems, but fill length is limited. Very thick TPE sections (over 6 mm) increase cycle time and risk voids due to compression during cooling. Nordmould reviews wall uniformity during DFM.
What does TPE injection moulding cost at Nordmould?
TPE tooling at Nordmould starts from €3,000. TPE resin is mid-priced compared with commodity plastics — softer specialty grades cost more per kilogram. For over-moulding projects, a two-component tool adds complexity and cost. Exact pricing is provided in a written quote after DFM review. Production runs start from 100 pieces.
What surface finishes work well on TPE parts?
TPE takes matt and soft-touch textured finishes extremely well; these finishes enhance the tactile quality that TPE is selected for. Glossy finishes are possible on harder TPE grades but are rarely specified — softer grades tend to show contact marks. Grain textures aligned with VDI or Mold-Tech standards can be applied.